Electric water heaters warm tap water through a heating element, which is immersed inside the tank. Electric heaters need to heat a large amount of water to ensure a sufficient supply of hot water, as the electric heater is not capable of heating water on demand. Another drawback of the electric heater is that the heating element is prone to burn-out, especially in hard water conditions. Sediment from dissolved calcium or other minerals in the water encases the heating element, eventually shorting it out.
Tank-less water heaters are also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters. Gas models do not have heating elements, but rather warm water with a burner instead. According to this arrangement, the gas water heater is able to provide hot water on-demand. However, gas water heaters are expensive to operate—even more so than electric heaters.
The use of heat pumps and heat exchangers for heating water boilers is not a new idea. Various types of heat pumps and/or heat exchangers are also known in the art. All of the systems known in the art suffer from one or more drawbacks including: the need for building a specialized system, use of gas or solar energy to heat the water and having a limited capacity for heating water, where the capacity for heating water is smaller than the use of the hot water such the water has to be heated before use—not for concurrent use.